考虑初始应力的坑侧土体真三轴试验研究

True triaxial experiment of foundation pit considering initial stress

针对基坑开挖过程中坑侧土体的应力路径,采用真三轴仪进行考虑初始应力状态下侧向卸荷试验,并与常规三轴试验以及轴向加荷真三轴试验结果进行对比分析,结果表明:q-εs曲线类似于常规三轴剪切试验的(σ1-σ3)-ε1曲线,呈双曲线关系;由于中主应力的影响,土体的初始强度得到提高,真三轴加荷试验初始切线斜率总是大于常规三轴试验的初始斜率;在侧向卸荷的条件下,土体可以在相对小的应变下发生破坏,加荷路径下破坏,土体应力强度要大于卸荷路径。

For the stress path of soil around pit in the excavation process, by using true triaxial apparatus the lateral unloading tests are carried out considering initial stress, and comparing routine triaxial test results with those of true triaxial test in lateral loading. Then some conclusions from analyzing contrastive results are made. The q-ε3 curve, which is hyperbolic relation, is similar to the （σ1-σ3）-ε1 curve of routine triaxial shear test. The incipient strength of soil with true triaxial apparatus has increase because of intermediate principal stress. True triaxial incipient tangent slope is always higher than that of routine triaxial test during loading. Soil sample unloaded in minor direction collapses at smaller strain. The stress strength of soil in loading path is bigger than that in unloading path.